The present invention relates to apparatus for testing cigarettes and other rod-shaped articles of the tobacco processing industry. More particularly, the invention relates to improvements in apparatus for ascertaining the presence or absence of defects at the exterior of rod-shaped articles of the tobacco processing industry, especially for detecting the presence or absence of smudges, open seams, holes and/or frayed ends, the presence or absence of imprints, improper application of imprints, the presence of absence of filter mouthpieces in filter cigarettes, cigars or cigarillos, the presence or absence of dents, flexure or bending of plain or filter cigarettes, cigars or cigarillos and/or filter rod sections, whether or not the uniting bands which connect filter mouthpieces to plain cigarettes, cigars or cigarillos are properly attached, departure of the outline of an article from round and/or a combination of such defects.
It is already known to monitor the exterior of rod-shaped articles of the tobacco processing industry while such articles form a single layer and advance sideways (namely at right angles to their respective longitudinal axes) on a testing conveyor, e.g., a fluted drum. The testing apparatus normally or often comprises optical testing means which can include a radiation source, means for focusing one or more beams of radiation upon the exterior of the article at the testing station, and means for evaluating radiation which is reflected by the exterior of the article because changes in the characteristics of radiation which is reflected by a cigarette or the like are indicative of the quality of the wrapper of such commodity. The just described conventional testing apparatus can be used to ascertain the condition of a wide variety of rod-shaped articles of the tobacco processing industry including filter rod sections, plain or filter cigarettes, cigars or cigarillos, cheroots or others.
The following description of the invention will refer primarily to filter cigarettes or plain cigarettes; however, it is to be understood that the apparatus of the present invention can be used with equal advantage for the testing of all kinds of rod-shaped articles of the tobacco processing industry.
It is customary to test successive plain or filter cigarettes after they issue from a cigarette rod making machine or in a cigarette making machine proper. Such final test is intended to allow for segregation of defective cigarettes from satisfactory cigarettes before the cigarettes are introduced into the packing machine or into storage so that defective cigarettes cannot reach the consumer. A drawback of presently known testing apparatus which are utilized for such purposes is that they cannot detect all defects which are, or are likely to be, present and which can be ascertained as a result of optical inspection of the exterior of the articles. For example, if the wrappers of cigarettes are tested by pneumatic means (which normally involves introduction of compressed air into one end of the article and monitoring the drop of pressure which is attributable to escape of testing fluid through open seams, holes or like defects in the wrapper of the article), such pneumatic testing cannot ensure the detection of all defects because a hole which happens to be sealed by a tobacco shred on by a piece of tobacco rib does not permit the escape of testing fluid even though it constitutes or can constitute a serious defect. Moreover, pneumatic testing cannot invariably lead to detection of many other types of defects which may not result in leakage of tobacco smoke through the wrapper but detract from the appearance of the product. Such defects include the presence of tobacco crumbs between those portions of wrapping material which form the customary longitudinally extending seam of a cigarette. Still further, if the articles to be tested are filter cigarettes, pneumatic testing cannot invariably reveal the quality of uniting bands which connect the filter plugs to the respective plain cigarettes. For example, a uniting band may extend partially beyond the general outline of the filter cigarette to thus detract from its appearance. Furthermore, a corner portion of a uniting band can be bent outwardly and such defect, too, cannot be detected by a pneumatic testing apparatus which is designed to establish a pressure differential between the interior and the exterior of the wrapper. Still further, pneumatic testing apparatus cannot detect dented, bent, flexed or otherwise mechanically deformed plain or filter cigarettes.
Attempts to detect the presence of defects which cannot be detected by pneumatic testing means include resort to optical testing means. Thus, it was already proposed to optically scan the exterior of the continuous cigarette rod which is turned out by a cigarette rod making machine and is thereupon subdivided into plain cigarettes of unit length or multiple unit length. A drawback of such proposal is that the optical testing apparatus cannot detect the presence of all defects which are likely to be present in the ultimate product, namely in plain or filter cigarettes of unit length or multiple unit length. This is due to the fact that many defects develop during and/or subsequent to subdivision of a continuous cigarette rod into plain cigarettes of unit length or miltiple unit length. Those defects which can arise subsequent to subdivision of the rod into discrete plain cigarettes can include holes, smudges, spots of adhesive extending outwardly beyond the seams, the absence of imprints, improperly applied imprints, improperly applied filter mouthpieces, denting, bending or flexing of articles subsequent to severing of the rod, and many others. Therefore, a production line which employs such optical testing apparatus must be equipped with additional testing apparatus which monitor the condition of the ultimate products, such as plain or filter cigarettes, in order to detect defects which are not detectable or do not exist at the time when the tobacco-containing portion of the ultimate product constitutes a coherent rod wherein a tubular wrapper surrounds a filler consisting of natural, reconstituted or substitute tobacco. On the other hand, optical testing of a cigarette rod exhibits the advantage that the entire exterior of the wrapper of the rod can be monitored upstream of the cutoff which serves to subdivide the rod into plain cigarettes of unit length or multiple unit length.
German Offenlegungsschrift No. 28 40 617 discloses an apparatus which serves for optical testing of the exterior of discrete rod-shaped products of the tobacco processing industry, particularly plain or filter cigarettes of unit length or multiple unit length. In accordance with the proposal in this German printed publication, successive cigarettes are transported individually into a testing zone and are brought to a standstill prior to beginning to rotate around their respective longitudinal axes through an angle of at least 360.degree.. This enables the optical testing instrumentalities to inspect the entire exterior of the article at the testing station. The testing apparatus normally comprises a source of radiation, means for directing radiation against the exterior of the rotating article at the testing station, and means for monitoring changes in the characteristics of radiation upon reflection because such cahnges are, or can be considered to be, indicative of the presence of one or more defects at the exterior of the tested article. This proposal exhibits the serious drawback that the testing operation takes up a considerable amount of time because each article to be tested must be transported to a predetermined testing station, its forward progress must be interrupted, and it must be set in rotary motion about its longitudinal axis in order to make sure that the testing apparatus can examine the entire exterior of the wrapper. Furthermore, the means for rotating the article at the testing station about its longitudinal axis is likely to subject such article to pronounced mechanical stresses, especially if the rotation through and angle of at least 360.degree. should be completed within a reasonably short interval of time. Consequently, the means for rotating the article at the testing station is likely to affect the appearance of the wrapper and/or to otherwise damage the wrapper as a result of transmission of torque thereto.
A different optical testing apparatus is disclosed in German Offenlegungsschrift No. 30 30 140. This apparatus is designed to monitor the exterior of the wrappers of cigarettes which are caused to move sideways on a suitable conveyor. The apparatus comprises means for directing light against the exterior of the article which passes through a testing zone, and a so-called linear camera is provided to evaluate the reflected radiation, i.e., the camera is designed to evaluate a strip or line of radiation which is reflected by the article at the testing location. A drawback of such proposal is that the apparatus is incapable of testing the entire exterior of the wrapper of a cigarette. Consequently, the apparatus cannot ensure the detection of any and all defects which are likely to occur in a cigarette and are apt to develop subsequent to subdivision of a continuous rod into discrete articles or are of the type which cannot be detected while the commodity which is being tested still constitutes a continuous rod. If the just discussed apparatus were to be designed to ensure adequate monitoring of the entire exterior of the wrapper of each of a series of cigarettes or the like, it would be necessary to provide means for rotating each article about its own axis, the same as described above in connection with the first-mentioned German printed publication. The disclosure of German Offenlegungsschrift No. 30 30 140 does not contain any proposal to rotate the articles about their respective axes while the articles are located at the testing station.